Fatty acid esters of glycidol in refined fats and oils

Discrepancies in the analysis of 3‐chloropropane‐1,2‐diol (3‐MCPD) esters can be explained by the hypothesis that in some refined oils significant amounts of fatty acid esters of glycidol (glycidyl esters) are present in addition to 3‐MCPD esters. Glycidyl esters were separated from triacylglycerols by gel permeation chromatography (GPC) and detected by gas chromatography‐mass spectrometry (GC‐MS). Six samples of palm oil and palm oil‐based fats were analyzed by GPC and GC‐MS. In chromatograms of all samples, significant peaks, retention time and mass spectra in conformity with self‐synthesized glycidyl palmitate and glycidyl oleate were detectable. Quantification of individual glycidyl esters was not possible because of a lack of pure standards. Concentration of ester‐bound glycidol in different samples of fats and oils was estimated using an indirect difference method. Glycidyl esters could be detected only in refined, but not in crude or native, fats and oils. The highest concentrations were detected in palm oil and palm oil‐based fats. In a palm oil sample, glycidyl ester concentration varied according to different deodorization parameters, temperature, and time, while 3‐MCPD ester concentration was relatively constant, indicating that mitigation of glycidyl esters possibly may be achieved by optimizing refining parameters.     

Comparison of experimental techniques used in lipid crystallization studies

Four methods were used to monitor the crystallization behavior of anhydrous milk fat (AMF), milk fat triacylglycerols (MF-TAG), and MF-TAG plus diacylglycerols (MF-DAG). The crystallization process was monitored by measuring the solid fat content, turbidity, and scattering intensity of the crystallizing material, as well as by imaging using polarized light microscopy combined with digital image processing. In general, induction times followed the order MF-DAG>AMF>MF-TAG for all techniques. However, the absolute value for the induction times differed substantially; on average 3 min by microscopy, 7 min by light-scattering spectroscopy, 13 min by turbidimetry, and 25 min by pulsed nuclear magnetic resonance. Microscopic imaging coupled to image processing proved to be the most sensitive method, suitable for the study of early events in the crystallization of fats.     

Specific molecular and colloidal structures of milk fat affecting lipolysis,absorption and postprandial lipemia

In milk fat, fatty acids are located at specific positions on the triacylglycerol backbone. The sn‐2 position contains most saturated long‐chain fatty acids, while the sn‐3 position contains short‐chain fatty acids. Moreover, these triacylglycerols are structured as milk fat globules surrounded by their native membrane containing phospholipids. This native structure can be modified by the dairy processes to generate various possible colloidal structures with milk fat. The structure of triacylglycerols and the milk fat ultrastructure can impact on fatty acid digestion and absorption, which has a potential effect on cardiovascular risk factors linked to postprandial hypertriglyceridemia. The review points out the impact of the triacylglycerol structure and the ultrastructure of milk fat on these risk factors.     

Determination of total polar material in frying oil using accelerated solvent extraction

During use, frying fats undergo chemical deterioration. This leads to the formation of compounds that are more polar than the triacylglycerols of the fat. Collectively these are called total polar material (TPM), and the mass concentration of TPM is used as an indicator of the quality of frying fats. According to official methods, the fat or oil is separated into polar and non‐polar fractions by preparative column chromatography (PCC). The chromatographic step is time‐consuming and needs large amounts of solvents. Here we show that the chromatographic step can be replaced by accelerated solvent extraction (ASE). This was demonstrated for high‐oleic sunflower oil in which potatoes, carrots and parsnips were fried. The materials separated by these two procedures are shown to be identical as judged by HPLC of the TPM. The two procedures show good agreement.     

Effects of Lipid Structure Changed by Interesterification on Melting Property and Lipemia

Interesterification or the randomization reaction changes fatty acid positional distribution and solid fat content of fats, which may consequently affect fat absorption and metabolism. It is well established that saturated fatty acids in the sn‐2 position of triacylglycerols (TAG) have better digestibility and lower postprandial chylomicron clearance compared to those in the sn‐1,3 positions in animal experiments. TAG structure is also shown to affect fasting lipid level and atherosclerosis in animals, but fat interesterification it has been shown to not affect fasting lipid level in human adults. However, its effect on postprandial responses is controversial. In this review, the complex results of studies of interesterification and lipemia were briefly discussed. More importantly, the confounding of two factors that are both changed by interesterification, TAG structure and solid fat content as the main limitation on understanding how interesterification affects lipemia is emphasized. Separation of the two factors is possible using paired fats as demonstrated. This paper also discusses some intriguing effects of fats having saturated fatty acids in the sn‐2 position and the need for future research.     

Method for characterization of triacylglycerols and fat-soluble vitamins in edible oils and fats by supercritical fluid chromatography

This study demonstrates the usefulness of capillary supercritical fluid chromatography (SFC) for the characterization of triacylglycerols of edible oils and fats. Triacylglycerols were separated according to the acyl carbon number and the degree of unsaturation on a 25% cyanopropyl/25% phenyl/50% methylpolysiloxane stationary phase. Valuable information concerning the triacylglycerol composition of berry oils was obtained, despite the overlapping of certain triacylglycerol peaks. Simultaneous analysis of fat-soluble vitamins and triacylglycerols is not practical by capillary SFC with flame-ionization detection because of the low concentration of naturally-occurring fat-soluble vitamins in edible oils. Therefore, higher loading of the sample, which led to overloading of triacylglycerols, was required to get reasonable peaks for fat-soluble vitamins. The method was applied to the characterization of triacylglycerols and tocopherols in sea buckthorn pulp and seed oil, and cloudberry seed oil without any sample purification prior to SFC. In addition, the stationary phase proved useful for separating the more complex mixtures of triacylglycerols found in milk fat and in fish oil.     

Short‐chain fatty acids as marker for the degradation of frying fats and oils

The determination of fatty acid composition by gas chromatography as a routine task is established in most laboratories dealing with oils and fats. The scope of this method can be enlarged for a preliminary quality control of used frying fats and oils, which is commonly characterized by the determination of polar compounds and polymerized triacylglycerols. However, for screening purposes the determination of the short‐chain fatty acids C7:0 and C8:0 can give an early indication about the quality of used frying fats and oils.     

Dietary triacylglycerol structure and saturated fat alter plasma and tissue fatty acids in piglets

Human and pig milk triacylglycerols contain a large proportion of palmitic acid (16:0) which is predominately esterified in the 2-position. Other dietary fats contain variable amounts of 16:0, with unsaturated fatty acids predominantly esterified in the 2-position. These studies determined if the amount or position of 16:0 in dietary fat influences the composition or distribution of liver, adipose tissue, lung, or plasma fatty acids in developing piglets. Piglets were fed to 18 d with sow milk or formula with saturated fat from medium-chain triglyceride (MCT), coconut or palm oil, or synthesized triacylglycerols (synthesized to specifically direct 16:0 to the 2-position) with, in total fatty acids, 30.7, 4.3, 6.5, 27.0, and 29.6% 16:0, and in 2-position fatty acids, 55.3, 0.4, 1.3, 4.4, and 69.9% 16:0, respectively. The percentage of 16:0 in the 2-position of adipose fat from piglets fed sow milk, palm oil, and synthesized triacylglycerols were similar and higher than in piglets fed MCT or coconut oil. Thus, the amount, not the position, of dietary 16:0 determines piglet adipose tissue 16:0 content. The effects of the diets on the plasma and liver triacylglycerols were similar, with significantly lower 16:0 in total and 2-position fatty acids of the MCT and coconut oil groups, and significantly higher 16:0 in the plasma and liver triacylglycerol 2-position of piglets fed the synthesized triacylglycerols rather than sow milk or palm oil. The lung phospholipid total and 2-position 16:0 was significantly lower in the MCT, coconut, and palm oil groups, but similar in the synthesized triacylglycerol group and sow milk group. The lung phospholipid total and 2-position percentage of arachidonic acid (20:4n-6) was significantly lower in all of the formula-fed piglets than in milk-fed piglets. The physiological significance of this is not known.     

Bleaching of edible fats and oils

Almost all fats and oils are subjected to so‐called bleaching during processing. Originally bleaching was only used to reduce the colour. Today, however, the bleaching step is used mainly to remove or convert undesired by‐products to harmless ones from fats and oils. This will guarantee that such compounds do not interfere with the processing and that the requirements for human food are being met.     

Synthesis and isolation of added‐value milk fat derivatives using lipase‐catalyzed reactions and supercritical carbon dioxide

Lipase‐catalyzed reactions and supercritical technology are powerful tools that can be effectively combined for the modification and processing of fats. In addition, both are “green” technologies, which can produce high‐quality, food‐grade products without the need of additional solvents. We show two examples in which milk fat was used as raw material for the production of added‐value derivatives: short‐chain fatty acid ethyl esters, which are natural flavor agents; and a diacylglycerol‐based, potentially superior dietary fat. In both cases we applied a combination of lipases and supercritical carbon dioxide extraction for the synthesis and separation of products.     

The effect of minor components on milk fat crystallization

Milk fat is composed of 97–98% triacylglycerols and 2–3% minor polar lipids. In this study triacylglycerols were chromatographically separated from minor components. Isolated diacylglycerols from the polar fraction were also added back to the milk fat triacylglycerols. The crystallization behaviors of native anhydrous milk fat (AMF), milk fat triacylglycerols (MF-TAG), and milk fat triacylglycerols with diacylglycerols added back (MF-DAG) were studied. Removal of minor components and addition of diacylglycerols had no effect on dropping points or equilibrium solid fat contents. Presence of the minor components, however, did delay the onset of crystallization at low degrees of supercooling. Crystallization kinetics were quantified using the Avrami model. Sharp changes in the values of the Avrami constant k and exponent n were observed for all three fats around 20.0°C. Increases in n around 20.0°C indicated a change from one-dimensional to multidimensional growth. Differences in k and n of MF-DAG from AMF and MF-TAG suggested that the presence of milk fat diacylglycerols changes the crystal growth mechanism. Apparent free energies of nucleation (ΔG_c,apparent) were determined using the Fisher-Turnbull model. (ΔG_c,apparent) for AMF was significantly greater than ΔG_c,apparent for MF-TAG, and ΔG_c,apparent for MF-DAG was significantly less than those for both AMF and MF-TAG. The microstructural networks of AMF, MF-TAG, and MF-DAG, however, were similar at both 5.0 and 25.0°C, and all three fats crystallized into the typical β′-2 polymorph. Differential scanning calorimetry in both the crystallization and melting modes revealed no differences between the heat flow properties of AMF, MF-TAG, and MF-DAG.     

Plastic fats with zero trans fatty acids by interesterification of mango,mahua and palm oils

Speciality plastic fats with no trans fatty acids suitable for use in bakery and as vanaspati are prepared by interesterification of blends of palm hard fraction (PSt) with mahua and mango fats at various proportions. It was found that the interesterified samples did not show significant differences in solid fat content (SFC) after 0.5 or 1 h reaction time. The blends containing PSt/mahua (1:1) showed three distinct endotherms, indicating a heterogeneity of triacylglycerols (TG), the proportions of which altered after interesterification. The SFC also showed improved plasticity after interesterification. Similar results were observed with other blends of PSt/mahua (1:2). These changes in melting behavior are due to alterations in TG composition, as the trisaturated‐type TG were reduced and the low‐melting TG increased after interesterification. The blends containing PSt/mango (1:1) showed improvement in plasticity after interesterification, whereas those containing PSt/mango (2:1) were hard and showed high solid contents at higher temperature and hence may not be suitable for bakery or as vanaspati. The blends with palm and mahua oils were softer and may be suitable for margarine‐type products. The results showed that the blends of PSt/mahua (1:1, 1:2) and PSt/mango (1:1) after interesterification for 1 h at 80 °C showed an SFC similar to those of commercial hydrogenated bakery shortenings and vanaspati. Hence, they could be used in these applications in place of hydrogenated fats as they are free from trans acids, which are reported to be risk factors involved in coronary heart disease. For softer consistency like margarine applications, the blends containing palm oil and mahua oil are suitable.     

Effect of PUFA at sn‐2 position in dietary triacylglycerols on the fatty acid composition of adipose tissues in non‐ruminant farm animals

The influence of the distribution of polyunsaturated fatty acids on the glycerol backbone of dietary triacylglycerols on the fatty acid profile of adipose tissue and muscle phospholipids was investigated in growing‐finishing pigs (48) and broiler chicken (84). The animals were fattened on barley/soybean meal diets supplemented with a blend of soybean oil and beef tallow, either in the ratio 3:1 w/w (high‐PUFA) or 1:3 w/w (low‐ PUFA). Part of the high‐ and low‐PUFA blends was chemically interesterified to randomly distribute all fatty acids over the three positions of the glycerol. Thus, two sets of diets of identical overall fatty acid composition, but differing in the distribution of fatty acids in the triacylglycerols, were fed. Growth performance and carcass composition were neither affected by fatty acid composition nor by randomisation of dietary fats in either animal species. Apparent digestibility of energy was slightly lower in pigs fed the low‐PUFA blends. Fatty acid profile of subcutaneous fat of pigs and broilers as well as of internal body fat (lamina subserosa) and muscle phospholipids of pigs varied according to the dietary fatty acid composition but was not affected by randomisation of dietary fats. These findings are explained in terms of the hydrolysis of TAG during transport of lipids from enterocytes to adipose tissue cells and the continuous lipolysis and re‐esterification of fatty acids that take place in adipose tissue cells.     

Validation of a gas‐chromatographic method for the determination of milk fat contents in mixed fats by butyric acid analysis

Gas‐chromatographic analysis of butyric acid (C4) in mixed spreadable fats can be used to calculate the milk fat proportion, either by additional analysis of the underlying pure milk fat (component sample) or by using a mean C4 content instead. After comparison of several analytical variants and subsequent development of an improved draft standard for quantitation of milk fat in mixed fats, this draft was checked for accuracy in three EU‐wide ring tests performed with 26 participating laboratories. Due to the natural variation of the butyric acid content in European milk fats, deviations from the actual milk fat content may amount up to ± 10% in addition to analytical errors when calculating with a mean C4 content instead of the C4 content of a component sample. Though the reproducibility could be improved by application of correction factors derived from a reference fat, only the calculation based on the additional analysis of a component sample of the pure milk fat led to an acceptable accuracy concerning the trueness of the results in combination with good repeatability (r) and reproducibility (R). Finally, several further improvements of the draft standard led to a precision of r = 4.3% and R = 6.0% relative to the mean of two milk fat contents determined. Thus, the tested procedure proved its suitability for a control method of the declared milk fat content in mixed fat spreads.     

Milk – A new source for bioactive phospholipids for use in food formulations

The fat globules of milk are surrounded by a membrane, which contains a triple layer of phospholipids. Concentrated cream is thus a very good raw material for further processing in order to make a powder, enriched in phospholipids. A powder can in this way easily be produced with 20% phospholipids using only common dairy processes such as centrifugation and membrane filtration. Milk phospholipids differ in compositions from existing commercial sources such as soybean lecithins and egg lecithins particularly with respect to the content of two bioactive phospholipids namely sphingomyelin (about 24%) and phosphatidylserine (12%). Sphingomyelin is an active agent controlling the intestinal uptake of cholesterol and triacylglycerols in human nutrition. Intake of phosphatidyl serine has clinically documented effects in maintaining cognitive performance like memory and stress control. A milk phospholpids enriched product thus offers a 100% natural alternative to the well‐established, semi‐synthetic head‐group exchanged phosphatidyl serine from soy lecithin now existing on the market for functional foods formulations.     

Production of High-Melting Symmetrical Monounsaturated Triacylglycerol-Rich Fats from Mango Kernel Fat by Acetone Fractionation

1,3‐Distearoyl‐2‐oleoyl‐glycerol, 1‐palmitoyl‐2‐oleoyl‐3‐stearoyl‐glycerol and 1‐stearoyl‐2‐oleoyl‐3‐arachidoyl‐glycerol are typical high‐melting symmetrical monounsaturated triacylglycerols (Hm‐SMT) found in cocoa butter improver (CBI). These triacylglycerols help to increase the hardness of chocolate products in tropical climates. In the present study, natural CBI products were produced from mango (Mangifera indica, Linn) kernel fat (MKF) by selective three‐stage fractionation using acetone. The second stearin (fraction I) from the first precipitate of MKF by fractionation for 180 min at 15 °C contained 86.9% of Hm‐SMT, and the third stearin (fraction II) obtained from fraction I by further fractionation for 180 min at 18 °C was enriched with 94.4% Hm‐SMT. High percentages of such triacylglycerols in these products contributed to higher slip melting points (36.5–37.7 °C) than commercial cocoa butter and cocoa butter equivalent (26.7 and 27.9 °C). Also, their differential scanning calorimetry properties and solid fat content values were superior to those in traditional confectionery fats, indicating that the tailored stearins could be used as ideal CBI. In particular, the hard fat blends consisting of 55–70% cocoa butter (CB) and 30–45% fraction II were considered as the preferred heat‐resistant chocolate ingredients. In addition, the mixture of the oleins (fraction III) was rich in diunsaturated and triunsaturated triacylglycerols and showed similar thermal properties to super palm oil, thus making it more suitable as special fat ingredients and modified fat sources.     

Characteristics of Mango Kernel Fats Extracted from 11 China-Specific Varieties and Their Typically Fractionated Fractions

11 China‐specific mango varieties, i.e., Tainong, Xiangya, Okrong, Keitt, Chiin Hwang, Guifei, Yuexi, Biantao, Guixiang, Zihua and Guire, were selected from South China, and the kernels were separated from pulps and then dried to extract mango kernel fats (MKF). 5.65–11.14 % of the fats could be obtained from dried kernels using hexane extraction, and their iodine values, slip melting points, triacylglycerols, sn‐2 fatty acids and micronutrients were analyzed. MKF were comprised predominantly of triacylglycerols reaching 85.09–92.72, and 78.28–84.37 % of oleic at the sn‐2 position. 29.99–55.44 % of SOS, 11.17–23.34 % of SOO and 13.10–19.79 % of POS occupied the main percentages of triacylglycerols, indicating MKF have diversified application after fractionation. Certain variety characterized as moderate values mentioned above, therefore, was selected and then fractionated by two‐stage processes to produce typical MKF fractions. The stearin (Fraction‐II) fractionated from the first solid fraction (Fraction‐I) with 68.09 % of SOS and 15.43 % of POS was more suitable as cocoa butter improver, while the olein (Fraction‐III) produced from the first liquid fraction was rich in SOO (45.59 %), POO (11.37 %) and OOO (11.14 %), which are considered as ideal cooking oil or frying fat ingredients. In addition, high amounts of micronutrients, including sterol, tocopherol and squalene, were also found in MKF ranged from 3837 to 7085, 81 to 916, and 164 to 941 mg/kg among different varieties, respectively. In particular, squalene levels were higher compared with most of other vegetable oils.     

Enzymatic biodiesel production: Technical and economical considerations

It is well documented in the literature that enzymatic processing of oils and fats for biodiesel is technically feasible. However, with very few exceptions, enzyme technology is not currently used in commercial‐scale biodiesel production. This is mainly due to non‐optimized process design and a lack of available cost‐effective enzymes. The technology to re‐use enzymes has typically proven insufficient for the processes to be competitive. However, literature data documenting the productivity of enzymatic biodiesel together with the development of new immobilization technology indicates that enzyme catalysts can become cost effective compared to chemical processing. This work reviews the enzymatic processing of oils and fats into biodiesel with focus on process design and economy.     

Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat

In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C₁₀−C₁₈ fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacyl-glycerol moieties of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C₄−C₁₈ fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding in polarity to the chloropropanediol diesters.     

Dietary lipids and arteriosclerosis

A great deal of attention has been given to the question of whether dietary fats in general and certain fats in particular play an important part in such arteriosclerotic complications as heart attacks and strokes. Milk fats have been widely accepted as desirable nutritional fats. Cow milk fat, or butter, contains a wide variety of fatty acid derivatives, including the important, medium chain acids. The structural configuration of butter triglycerides facilitates absorption of the palmitate present in butter. However, there have been objections to the use of butter and other forms of milk fat because of the preoccupation of many investigators with the unproven lipid theory of arteriosclerosis, and because serum cholesterol levels are relatively high after the intake of milk fat. Reevaluation of the lipid theory suggests that cholesterol can hardly be an atherogenic factor. Cholesterol occurs under conditions of tissue repair, and it may well be that the high serum levels in arteriosclerotic conditions are a consequence of such processes. The low serum levels occurring after the consumption of polyunsaturated vegetable oils are often associated with high tissue levels of cholesterol. Long term clinical studies and population surveys suggest that this century’s changes in mortality and morbidity are much less related to dietary factors (other than over-eating) than is claimed. New insights in the fields of immunology and microbiology may be vastly more important for an understanding of some etiological factors in arteriosclerosis.